48 healthy subjects are enrolled. The study is a single-blind. In this study, under supervision of study investigators, a single dose of Injectable Extended-Release Naltrexone (380 mg), test or reference is administered intramuscularly to healthy subjects. For the measurement of pharmacokinetic parameters, 5 ml blood samples are taken before (0 min) and at 1, 2, 4, 8, 12, 24, 32, 38, 48 and 58 hours and 3, 5, 7, 10, 14, 18, 24, 30 days after administration.